I have been lucky enough to be part of 3 Beaucastel verticals that have included both the 89 and 90. They were always opened, decanted and poured within an hour. They seemed ready to go on opening.
The other bottles usually were treated the same way. During the summer I opened a 2015 and decanted it, we poured it almost right away and it was tremendous. Young but open.
I would not do anything other than open and pour that 89. It looks like it has been slow oxing for at least a decade.
I do, yes! Just got one as a birthday gift 
I’m looking forward to seeing the notes :)! Hope you enjoy
I hadn’t seen this thread but happened to open a 2001 tonight, it’s still in front of me. Not sure it needs to be decanted but make sure you can leave some to see it develop. First glances had me worried about mild cork issues, but it’s opened widely with great spice and perfume after an hour.
Went to a tasting a few years back and brought a 1999 right from the wine refrigerator and it was pretty cloudy throughout the night and didn’t show well. Would definitely stand them up several hours before whether you decant or not.